Time delay switch



April 12, 193s. C.' H. LARSQN V TIME DELAY SWITCH Filed 0G13. 17, 1934 flvnfp/HTHY HFrfe Patented Apr. l2, 1938 UNITED STATES PATENT OFFICE Adlake Company, a

corporation of Illinois Application october 17, 1934, serial No'. 748,586

8 Claims.

.'I'his invention relates to switches that are operated to open or to close a circuit when something happens, or some condition arises that makes a change in a circuit desirable, but only after a delay or time interval that is a matter of selection under the particular circumstance, and the principal object oiA the invention is to enable the switch maker to easily and cheaply insure that each switch will have the particular l0 delay selected for a good use.

This is achieved in magnetic displacer mercury tube switches chosen to illustrate the invention by making the delay period depend upon the-time required for a given quantity of gas to iiow through the space obstructed by a wad of ilber whose resistance to the flow of gas depends upon the thickness oi the wad and how tight it is packed, both of which are quickly determined by skilled workmen.

In the drawingzy yFig. 1 is a vertical section through a xed tube mercury switch of. what is called the front contact type in which the mercury is displaced by the attraction of a cylindrical armature to an electro-magnet, and thearmature carries with it a displacer tube open at the bottom to mercury and at the top to the gas illl, and is constricted between the openings by a wad of cotton, asbestos, or the like; in this gure, the parts are shown in the position they assume when the magnet is de-energized for longer than the time delay period.

Fig. 2 is a vertical section similar to Fig. 1 showing the eiIect of constricting the hollow displacer when the armature is drawn down;

Fig. `3 is a view similar to Fig. 1 showing how after the time delay interval the mercury rises within the displacer and closes the circuit;

Fig. 4 is a view similar to Fig. 1 showing how some mercury is lifted with the displacer when the magnet is de-energized and the displacer rises;

Fig. 5 is a vertical section of a back contact switch in closed position;

Fig. 6 is a vertical section through the same'A switch immediately after the magnet is enersized:

Fig. 7 is a vertical section through the same switch immediately after the magnet is deenergized:

Fig. 8 is a vertical section through the upper part oi' the displacer tube and three wads oi cotton separated by layers of powder; and

Figs. 9 and 10 are vertical sections through the upper portion of the displacer tube, and a tool used for packing the wad in the tube.

But these forms are here used because they are simple and clearly illustrate the principle oi the invention, which others will readily apply to a variety of switches in which the restricted flow of gas can determine the time delay.

A glass envelope III has lead-in wires Il and i2 sealed through it and equipped with electrodes I3 and il to cooperate with puriiled mercury i5. The lead-in wire Il is shielded by a glass tube I6 to a suitable height and then bent overl to form the electrode Il. The armature I1 is a cylinder of soit iron-in this instance, Swedish iron known 'as Svea.` It telescopes with clearance over a glass tube I8 (although ceramic or any non-magnetic material may be used) having a wide open end I9 to the mercury at the bottom and a spherical head 20 provided with a small opening 2| for gas at the top. The armature l1 and the displacer tube i8 are held in assembled relation by helical springs 22 whichfrictionaily engage the projecting ends of the displacer tube.

Within the upper end, in this instance and always where the gas is to flow, there is a wad 23 of cotton (or asbestos orany other liber that will pack and will not react with themercury) packed against the spherical head 20 and having a thickness and density determined by the desired time delay interval.

The envelope I0 is adjustably mounted within the pole sleeves 24 and 25 oi' an electromagnet 26 by a split brass sleeve 2l that grips the envelope and has its bottom end resting on top of the sleeve 25.

In a. front contact switch when the magnet is energized, the parts assume some such position as shown in Fig. 2, in which the gas 1111 in the area 28 of the hollow displacer tube is trapped and compressed, forcing the mercury downwardly within the displacer tube to a position about like that indicated at` 29. As the gas permeates the wad 23 and escapes to the upper portion of the envelope, the pressure differential on the mercury within and without the displacer gradually equalizes and the mercury rises within the displacer to about the position Il, shown in Fig. 3, closing the switch.

When the magnet is de-energized, the arma- Fig. 4) until the flow through thewad 2l allows the pressures to be equalized when the mercury assumes the position shown in Fig. 1 again, and the circuit is broken.

In a similar fashion, Figs. 5, 6 and '7 illustrate approximately the position the mercury takes in a back contact switch; in Fig. when the circuit is closed; in Fig. 6 immediately after the magnet has been energized; and in Fig. '1 after the magnet has been de-energized.

The quantity of the fiber in the wad and the degree of pressure and the lmannerdn which it is applied will depend partly on the nature of the fiber and partly on the time delay required. The best grades of sterilized absorbent cotton on sale at drug stores have been found very satisfactory. It can be f ormed into wads with the ngers and pushed to position in the displacer tubes with any sort of rod. However, it is best to use a tool that will pack the edges somewhat, as illustrated at 35 in Fig. 10, for the nature of the material causes it to grip the walls of the tube and retain a residual compactness after the tool has been removed. In some instances, it has been found useful in making the correct time delay to insert a plurality of wads in succession, pressing each down tightly as it is put in place. Where very long delay is required, powder in a layer 36 between the wads assists in constricting the flow. Alundum, carborundum, cinchonium oxide, ground glass, or, generally, any ceramic or siliceous powder that will not react with mercury will be found satisfactory-the iiner the powder, the greater the constriction.

The last wad of cotton should be trimmed and singed to remove frayed hairs before forcing it home.

When asbestos is used, it should be burnt or otherwise purified to prevent injury to the mercury. Other fibres should have appropriate purification for the same reason.

By way of illustration of proportions, one front contact switch embodying the invention has an envelope 141/2 mm. inside diameter and 128 mm. long. The armature is 1% long, 5% outside diameter and 23/64 inside diameter. The displacer tube is 3 long, 81/2 mm. outside diameter, 61/2 mm. inside diameter, with a hole at thetop 5/64" in diameter.

I claim as my invention:-

1. In a mercury tube switch relay, a sealed tube containing electrodes, a charge of mercury, a gas ll, a displacer including a long hollow body having a wide opening presented to the mercury and another opening to the gas, and means to retard` the flow of gas into and out of the body above the mercury including a wad of fiber in the body of suiilcient thickness and density to effect the desired delay.

2. In a time delay relay of the class described, a sealed tube containing electrodes, a charge of mercury, a gas ll, a displacer including a tube open at the bottom to mercury and at the top to gas, and a wad of fiber packed against the top of the tube and of suilicient thickness and density to effect the desired delay.

3. In a time delay relay of the class described, a sealed tube containing electrodes, a charge of mercury, a gas iill, a displacer including a tube open at the bottom to mercury and at the top to gas, and a wad of fiber packed in the top of the tube to retard the iiow of gas into and out of the tube, the gas opening being of suiiicient size to permit substantially unrestricted iiow of gas into and out of the tube.

4. In a mercury tube switch, an envelope, electrodes sealed through the envelope, a gas lill, a charge of mercury within the envelope to cooperate with the electrodes and control the circuit, means to shift the mercury to change the condition of the circuit, and means to delay the change comprising a hollow body having a passage for gas and a wad of fibrous material in the passage of such thickness and density as to retard the flow of gas for a time corresponding to the delay.

5. In a mercury tube switch, an envelope, electrodes sealed through the envelope, a gas ll, a charge of mercury within the envelope to cooperate with the electrodes and control the circuit, means to displace the mercury to change the condition of the circuit, and means to delay the change comprising a hollow body open tothe gas and mercury at spaced points and means to vary the pressure on the mercury within the body including a wad of iiber to retard the flow of gas said ber being of suillcient thickness and density to account for at least a substantial portion of the time delay desired.

6. In a mercury tube switch, an envelope, electrodes sealed through the envelope, a gas iill, a charge of mercury within the envelope to cooperate with the electrodes and control the circuit, means to displace the mercury to change the condition of the circuit, and means to delay the change comprising a hollow body having an opening below for mercury and above for gas and means to restrict the flow of gas and thereby control the period of operation comprising a wad of ber in the hollow body of suicient thickness and density to account for at least a substantial portion of the time delay desired.

7. In a mercury tube switch, an envelope, electrodes sealed through the envelope, a gas 1111, a charge of mercury within the envelope to cooperate with the electrodes and control the circuit, a displacer in the envelope including a glass tube open below to the mercury and above to the gas, and means to restrict the flow of gas including a wad of fiber in the upper portion of the tube and packed suillciently to 'account for at least a substantial portion of the time delay desired.

8. In a mercury tube switch, an envelope, electrodes sealed through the envelope, a gas fill, a charge of mercury within the envelope to cooperate with the electrodes and control the circuit, means to displace the mercury to change the condition of the circuit, and means to delay the change comprising a hollow body having a passage for gas and a quantity ofpowder in the passage, the powder particles being of such quantity and size and so packed together as to account for at least a substantial portion of the time delay desired. y

CARL H. LARSON. 

